Stihl MS 400 C-M (Fuel Consumption Test)
There is no single reliable fuel-use figure for the STIHL MS 400 C-M: consumption changes with wood, chain sharpness, bar setup, and cutting method. To measure your saw, use fresh 50:1 premix, a repeatable cutting load, and measured refills. Record fuel used and cutting time, then report litres per hour and the test conditions.
Are you comparing fuel use to estimate run time or to check whether a saw is using too much? Either way, a number without its test conditions can mislead. In my product-evaluation work, I treat fuel consumption as a test result, not a fixed specification. The method matters as much as the measurement.
What a fuel-use test can tell you
Fuel consumption is the amount of premix the saw uses during a defined task. A useful result links that amount to time or completed cuts. It can help you compare repeat tests on the same saw, but it cannot predict every workday or prove that one saw is more efficient than another under different loads.
The MS 400 C-M has a 66.8 cm³ engine, rated power of 4.0 kW, and a 0.60 L fuel tank. Those specifications describe the machine; they do not state how long a tank will last. A tank can empty faster in heavy wood or slower during lighter cutting.
For a fair result, keep the wood, cutting time, operator, and cutting equipment as consistent as possible. Report the conditions with the number. Without them, litres per hour may sound precise while saying little about how the saw performed.
Why there is no universal consumption number
A consumption figure is meaningful only when you know what the saw was doing. Cutting hardwood at a steady pace is not the same task as making short cuts in softwood, and neither matches idling or moving between trees. Bar length and chain condition can also change the load.
A controlled test can show whether your saw’s use changes over time under similar conditions. It cannot give a guaranteed runtime for a different job. Use the tank capacity as a volume limit, not as a runtime promise.
Set up the saw and test safely
A repeatable test begins with a saw in sound working order and a cutting setup suited to the wood. The MS 400 C-M is a professional saw intended for ground-based timber cutting, but displacement alone does not determine a safe bar choice. Follow the operator’s manual for the exact model and market version.
Use a bar and chain approved for the saw. Match chain pitch, gauge, and drive-link count to the bar markings and saw’s sprocket. Do not infer the chain gauge or depth-gauge setting from pitch alone. Follow the chain maker’s specifications for sharpening angles and depth gauges.
Before each run, check chain tension and lubrication. Inspect the chain brake, throttle interlock, stop switch, chain catcher, handles, and bar-oil supply. Confirm that the chain is sharp, correctly fitted, and undamaged. Use STIHL bar-and-chain oil or an approved equivalent; oil flow is adjustable, so it should not be treated as a fixed fuel-use figure.
Wear chainsaw PPE: helmet with eye and hearing protection, chainsaw leg protection, gloves, and protective footwear. Secure the workpiece so it cannot roll or shift. Keep people outside the work area. If felling is involved, follow the site plan, maintain escape routes, and work within your training and applicable ANSI Z133 and OSHA requirements. A fuel test does not qualify a saw or operator for felling.
| Item | What to confirm before testing |
|---|---|
| Fuel | Fresh premix at 50:1, using STIHL two-stroke oil or oil approved by STIHL |
| Bar and chain | Approved for the saw; pitch, gauge, and drive links match their markings |
| Chain | Sharp, correctly tensioned, and set to the chain maker’s specifications |
| Lubrication | Correct bar oil present; oil reaches the chain using the manual’s safe check |
| Work area | Wood is stable; bystanders are clear; PPE is worn |
The manual’s listed idle speed is 2,800 rpm. Do not use unloaded, prolonged wide-open-throttle running as a substitute for cutting; it does not represent a useful cutting test and may be unsafe.
Measure fuel use with a repeatable cutting test
A field test needs a known starting fuel level, a consistent load, and a measured end point. Choose either a fixed test duration or a fixed number of cuts. Keep the operator, wood type and size, cutting method, and saw condition as steady as you can.
Step-by-step test method
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Record the baseline. Note the fuel type, ambient conditions, wood species, diameter and moisture if known, bar and chain setup, and chain sharpness. Record the starting fuel level or measure a set quantity. Keep chain oil separate from fuel measurements.
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Prepare the load. Select safely supported wood that you can cut in a consistent way. Use the same pieces or a closely matched load for each run. Do not compare results as if equivalent when wood size, species, or moisture differs.
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Run the saw as directed. Start and warm it according to the operator’s manual. Use a sharp chain and controlled feed. Record elapsed cutting time and cut count. Stop if the workpiece moves, the chain stops receiving oil, power drops, or the saw makes an abnormal sound.
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Measure the fuel used. Shut down and let the saw cool before refueling. Measure how much fuel is needed to restore the same starting level. Do not refuel a hot saw. Record the amount and repeat the test only if the equipment and load remain safe and comparable.
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Calculate and report. Convert the test time to hours, then divide fuel used in litres by elapsed time in hours. If useful, divide fuel used in millilitres by completed cuts.
L/h = fuel used (L) ÷ elapsed test time (h)
mL/cut = fuel used (mL) ÷ completed cuts
A hypothetical calculation can show the math without claiming a measured MS 400 C-M result: if a test used 0.12 L in 0.20 hours, the rate would be 0.60 L/h. That number would apply only to that test and its conditions. It is not a factory rating or a forecast for another job.
Test scenarios to document, not assumed results
These scenarios show how to make comparisons useful. They are test plans, not reported measurements. Keep the method safe, and do not push the saw to finish a target if the wood or setup becomes unstable.
| Scenario | Hold steady | Record | What the result can show |
|---|---|---|---|
| Fixed-time run | Wood type and size, operator, chain setup | Fuel used, time, cut count | Fuel use during that defined task |
| Fixed-cut run | Number and approximate size of cuts, wood, setup | Fuel used, elapsed time | Fuel per cut for that wood and method |
| Repeat check | Conditions from an earlier run | Same data points each time | Whether use changed under similar conditions |
For a comparison between two saws, match the work, not just the clock. Use similar wood and cutting equipment, and report differences in bar and chain setup. A result from a short, light-cut test should not be compared directly with a long run in larger or harder wood.
Read the result and check for causes
A high fuel-use result does not by itself mean the saw has a fault. Heavy cutting, dull chain, poor cutting technique, or different test conditions can raise fuel demand. A low figure is not automatically better if the saw was doing less work or the test conditions changed.
Compare repeat measurements from the same saw under closely matched conditions. If consumption changes sharply, first check the fuel, filter, spark plug, chain, and bar setup as directed in the manual. Clean the air filter and cooling-air passages on the schedule given by STIHL. Replace damaged or overly worn cutting parts.
The C-M designation refers to electronically managed M-Tronic carburetion. Do not apply generic carburetor-screw adjustments. Use STIHL service procedures, and seek authorized service or required diagnostic equipment if basic checks do not explain poor running. Treat fuel use as a clue, not a tuning target.
If the engine loses power or behaves abnormally, stop the test. Straight gasoline, an incorrect oil ratio, or stale or contaminated fuel can lead to poor lubrication or abnormal combustion and damage the piston and cylinder. Verify fresh 50:1 premix; if internal damage is suspected, have the saw inspected before using it again.
Store fuel and saw safely between tests
Fuel condition affects both safe operation and the value of a later test. Use fresh premix during operation, and follow the operator’s manual for fuel-system steps before storage. Keep fuel in an approved, labeled container away from ignition sources. Do not leave stale fuel in the saw.
After testing, clean the saw and bar groove, inspect for damage, and store the powerhead and cutting equipment safely. Follow the manual for extended storage and cold-weather preparation. When you test again, note any change in fuel, chain, filter, or cutting conditions so the result remains interpretable.
Conclusion: report conditions with the number
A careful fuel-use test on the MS 400 C-M gives you a result tied to a specific job, not a universal runtime claim. Measure fuel used, record elapsed cutting time and cuts, and include wood, weather, chain, bar, and fuel details. Repeat only under similar conditions; investigate changes before adjusting anything.
FAQ
What is the fuel consumption of the MS 400 C-M?
There is no single consumption rate that applies to every task. Wood, load, chain sharpness, and operating method all affect fuel use. Measure your own saw under defined conditions and report litres per hour or millilitres per cut with the test details.
How large is its fuel tank?
The listed fuel-tank capacity is 0.60 L. Capacity alone does not determine runtime because the engine’s fuel demand changes with cutting load and conditions.
What fuel mix should I use?
Use a 50:1 premix with STIHL two-stroke oil or oil approved by STIHL. Follow the operator’s manual for the exact model and market specification. Do not run straight gasoline or an unapproved mixture.
How do I calculate litres per hour?
Divide the fuel used in litres by the elapsed test time in hours. For example, 0.12 L used over 0.20 hours equals 0.60 L/h for that test only.
Can I estimate cuts per tank?
Only for a similar wood type, cut size, chain condition, and cutting method. Record actual fuel use and cuts in a controlled test; do not treat a result from one load as a guarantee for another.
Does bar length change fuel use?
It can affect the work the saw performs and the load during cutting. Choose only a bar and chain approved for the saw, and compare results only when the cutting setup and wood are comparable.
Should I use chain oil when measuring fuel?
Yes. Keep bar-and-chain oil separate from the fuel measurement. Check that the chain receives oil, but do not count adjustable oil flow as fuel consumption.
What can cause unusually high fuel use?
A heavier load, dull chain, poor cutting technique, or different test conditions can raise fuel use. Check fuel quality, filter, spark plug, and chain condition as the manual directs. Seek STIHL service for unresolved running problems.
Can I adjust the carburetor to lower consumption?
Do not use generic carburetor-screw settings. M-Tronic manages carburetion electronically. Follow STIHL service procedures, and use authorized service or diagnostic equipment when needed.
Is it safe to refuel immediately after testing?
No. Shut the saw down and allow it to cool before refueling. Stop testing if power drops or the engine behaves abnormally, and check for correct fresh premix before further use.
(This article was written by one of our staff writers, Marcus Thorne. Visit our Meet the Team page.)
